1. Field of the Invention
The present invention relates to an optical image detecting structure with multiple functions. In particular, this invention relates to a multiple function optical image detecting structure that obtains the moving distance and direction of a tracing ball to calculate its displacement.
2. Description of the Related Art
Desktop personal computers or laptops usually use a mouse or a tracing ball device to control the cursor to move on the screen. An optical mouse is a common and popular such mouse. FIG. 1 shows a cross-sectional view of an optical mouse of the prior art. The optical mouse moves on a plate surface. The light-emitting element 81 emits light to a first reflection surface 821 of a light-guiding board 82 and the light is reflected to a second reflection surface 822. Next, the light is reflected by the second reflection surface 822, passes through the opening of the bottom shell 83, is projected onto a contacting surface 84 formed by a non-transparent medium, and is overlapped to an image axial F. The image on the image axial F is focused by a lens 85. Thereby, an image sensor 86 obtains the image on the image axial F formed by the light of the contacting surface 84. The image sensor can continuously obtain the exact image, and a circuit control unit (not shown in the figure) can calculate the moving distance and direction of the optical mouse and control the cursor to move on the screen.
The light axial D of the projecting light and the light axial R of the obtaining image have to form a crossed point P on the image axial F of the contacting surface 84 for the image-obtaining method of the optical mouse of the prior art. Thereby, the image sensor 86 can exactly obtain the image signal on the image axial F.
As shown in FIG. 2, the functions of the optical mouse are limited due to the type of the contacting surface 84, for example, the contacting surface 84 is made of a transparent material (such as a glass), or a material that can absorb/disturb light (such as a lacquered metal or a lens). When the contacting surface 84 is made of a transparent material, the contacting surface 84 does not overlap with the image axial F. When a light is projected onto the contacting surface 84 and the reflective index is not calculated, the light axial D of the projected light and the image axial F form a crossed point M. This means that the light axial D of the projected light and the light axial R of the obtaining image don't form a crossed point on the image axial F. Thereby, the function of the optical mouse fails. In other words, due to the type of the contacting surface 84, the function of the optical mouse is limited or fails.
The tracing ball device can be installed in the shell of the keyboard or the laptop, or is connected with the computer host by a USB connector. Next, the user uses his or her fingers to rotate the tracing ball to control the cursor to move on the screen.
The tracing ball device of the prior art is an optical type of tracing ball. Taiwan patent M258357, published on 1 Mar. 2005, discloses an optical tracing ball structure, as shown in FIG. 3. From the top surface towards the bottom surface of the shell 91, a base 92, a tracing ball 93, a light-passing board 94, an optical base 95, a circuit board 96, a light-emitting element 97, a light mask 98, and an identifying element 99 are located in the shell 92. The optical base 95 includes a lens 951, a reflection portion 952, and a light-guiding lens 953.
When the light generated from the light-emitting element 97 is projected onto the light-guiding lens 953 of the optical base 95, the light is reflected by the reflection portion 952 and is slantedly projected onto the bottom spherical surface of the tracing ball 93 (having a projection angle θ). The identifying element 99 detects the moving distance and direction of the tracing ball 93 via the lens 951. When the tracing ball 93 is rotated, the identifying element 99 detects the moving distance and direction of the tracing ball 93 and a displacement is calculated. The calculated displacement is transmitted to a host. Thereby, the host controls the cursor to move on the screen by referring the displacement.
Actually, after the light of the light-emitting element 97 is reflected by the reflection portion 952 and is projected onto the bottom spherical surface of the tracing ball 93, an image-obtaining area 931 is generated on the spherical surface. Reference is made to (A) and (C) of FIG. 3. The identifying element 99 obtains the image projected on the image-obtaining area 931 via the lens 951. The preexisting condition for the identifying element 99 to obtain the image is that the light has to be uniformly projected onto the spherical surface of the tracing ball 9 (this means that the light on the image-obtaining area 931 has to be uniform). Thereby, the identifying element 99 can obtain a complete image, and determine the moving distance and direction of the tracing ball 93 so that a displacement is calculated. Therefore, the cursor can be exactly controlled to move on the screen.
However, when the light of the light-emitting element 97 forms a light beam L that is emitted to the spherical surface of the tracing ball 9, a light-projecting area 932 is generated, as shown in (A), (B) and (C) of FIG. 3. Due to the inclined projection angle θ, the light-projecting area 932 and the image-obtaining area 931 cannot uniformly/overlap. Therefore, a shaded area 933 is generated on the image-obtaining area 931, as shown in (C) and (D) of FIG. 3. The identifying element 99 cannot obtain complete image to determine the moving distance and direction of the tracing ball 93 and calculate a displacement. (Part (D) is an enlarged figure of part D in Part (C) in FIG. 3.)
Reference is made to (A) and (B) of FIG. 3. When the projection angle θbecomes larger, the shaded/shading area 933 also becomes larger. As shown in (C) of FIG. 3, the shaded area 933 in the image-obtaining area 931 is (so) large that the complete displacement cannot be obtained. Therefore, the tracing ball device cannot obtain the exact displacement.